Method of preparing powdered refractory metals for mechanical working



METHOD OF PREPARING POWDEREl) REFRAC- TORY METALS FOR MECHANICAL WORKNG Application February 25, 1954 Serial No. 412,668

1 Claim. (Cl. 29-420) No Drawing.

The present invention relates to the cladding or sheathing of a base structure and a method of providing same.

Sheath rolling of titanium, Zirconium or beryllium powders is a commonly employed method in the art and in the practice of the method metallic powders are pressed to a desired shape, are enclosed in an iron tube of thin wall construction, the air within the tube is replaced with an inert gas, and the tube is. then welded shut. By this arrangement the powders may be handled while at elevated temperatures without special atmospheres.

Several objections are encountered in the practice of this process, however, since the lit of the sheath is not always good. and wrinkling and'folding occur during working. This leaves a deformed product when the sheath is subsequently removed by chemical or mechanical means.

It has also been the practice to electrodeposit coatings to structures formed of metals or nonmetals in order to impart oxidation resistance, electrical conductivity, etc. In many such uses either the surface or the coating is not compatible with the other or with electrodeposition and it has been found that with electrodeposition an appreciable thickness such as 0.2 inch is diflicult to achieve for many oxidation resistant alloys.

In the present invention it is proposed to provide a clad or sheath adaptable for oxidation or corrosion resistance without the necessity for alloying which in many cases is impossible or undesirable due to such side eflects as embrittlement.

In the practice of the present invention it is proposed that a structure be formed by placing solid or pressed metal or a mixture of metal and nonmetal powders in a tight-fitting metal sheath of the desired configuration, encasing the assembly in a rubber bag or container which is closed by a suitable watertight stopper and then subjecting the assembly to a hydrostatic pressure ranging from a few hundred to 60,000 pounds per square inch, depending upon the properties of the elements. Where the structure is to be used in sheath rolling the resultant tightly gripped metal may be fully enclosed by welding or brazing the open end of the sheath and the result will be'a container of minimum air or gas space. of course United States Patent the practical thickness of the sheath is limited by the hydrostatic pressure to be employed and it has been found that the sheath may be 0.2 inch or more in thickness for nickel when 60,000 pounds per square inch pressure is employed.

When it is proposed to utilize the oxidation resistant coating or property imparted by the surface metal and maintain the strength or other property of the enclosed metal it may be used in that form without removal of thecoating, or, when desired, the assembly may be further mechanically worked to increase the tightness of the sheath on the structure or to improve the mechanical properties of the finished product.

As an example, it has been found that a bar of molybdenum of unusual shape may be enclosed in a tube of Inconel to obtain the superior strength of molybdenum at 1000 C. combined with the oxidation resistance of Inconel.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

The method of preparing powdered refractory metals for mechanically Working comprising the steps of forming a unit by pressing powdered refractory base metal into solid form and encasing same within a deformable tubular member composed of corrosion resistant metal, the Wall thickness of said tubular member being substantially 0.2 inch and in tight-fitting relationship with the base metal, enclosing said unit with a tight-fitting flexible rubber-like container, sealing said container to provide a fluid tight assembly, subjecting said assembly to a high fluid pressure in all directions and within a range of 1,000 to 60,000 pounds per square inch to unite said tubular member and the base metal, whereupon the base metal is prepared for subsequent mechanical working.

OTHER REFERENCES Titanium, Report of Symposium on Titanium, March 1949, pages 27-30, published by Olfice of Naval Research, Washington, DC. 

